# Infinite universe? **URL:** \ **Category:** Great Debates\ **Created:** [January 3, 2026, 5:54am UTC](https://boards.straightdope.com/t/infinite-universe/1026295 "2026-01-03T05:54:35Z")\ **Posts on this page:** 20\ **Page:** 5
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [January 3, 2026, 9:54pm UTC](https://boards.straightdope.com/t/infinite-universe/1026295/81 "2026-01-03T21:54:21Z")
> [@xtenkfarpl](#): > > But the question is, are we asking in the right way? I am not sure how we can answer that without more observational evidence supporting or contradicting string theory, and concerning the nature of dark energy. ---
**Author:** ![Half\_Man\_Half\_Wit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/half_man_half_wit/32/21766_2.png) [@Half\_Man\_Half\_Wit](https://boards.straightdope.com/u/Half_Man_Half_Wit)\ **Post date:** [January 3, 2026, 10:05pm UTC](https://boards.straightdope.com/t/infinite-universe/1026295/82 "2026-01-03T22:05:07Z")
> [@Mijin](#): > > But again we have no reason to think any computation is happening, so this equivalence is irrelevant to making an empirical claim. What I’ve said doesn’t depend on whether there is computation happening, just that one model of producing random numbers is via infinite computations as described, and that having access to randomness allows computations otherwise feasible with such infinite means. But in the end, any scientific modeling is just coming up with a structure capable of reproducing observed phenomena, so to the extent it does that, it’s a perfectly good model of the phenomena. That’s not to say no other model might be possible, of course. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 3, 2026, 10:08pm UTC](https://boards.straightdope.com/t/infinite-universe/1026295/83 "2026-01-03T22:08:43Z")
My advice, just ignore the String Model entirely, until and unless it can make some actual testable predictions and those predictions are tested. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [January 3, 2026, 10:19pm UTC](https://boards.straightdope.com/t/infinite-universe/1026295/84 "2026-01-03T22:19:08Z")
Isn’t part of the problem that String Theory is untestable? Not a lack of tech that may come someday but literally untestable forever? ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [January 3, 2026, 10:25pm UTC](https://boards.straightdope.com/t/infinite-universe/1026295/85 "2026-01-03T22:25:17Z")
There are tests that could find evidence for aspects of string theory - but so far they’ve failed Here’s a report on one [test](https://www.scientificamerican.com/article/string-theorys-extra-dime/) > If extra dimensions of space exist, they must be smaller than about half the width of a human hair, according to new measurements of the strength of gravity at short distances. Researchers found that the same law governing the gravitational pull between planets continues to work when objects are separated by as little as 56 micrometers. The finding rules out extra dimensions of 44 micrometers or larger, they report in this week’s _Physical Review Letters_. I don’t know whether String Theory is _disprovable_ - you could always add a new reason that the expected evidence didn’t show up. But that’s a classic problem with science - what counts as disproving. ---
**Author:** ![Johanna](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johanna/32/8318_2.png) [@Johanna](https://boards.straightdope.com/u/Johanna)\ **Post date:** [January 3, 2026, 10:50pm UTC](https://boards.straightdope.com/t/infinite-universe/1026295/86 "2026-01-03T22:50:19Z")
> [@xtenkfarpl](#): > > The key take-home is that in a mathematical sense, some infinities are strictly larger than others. When I was 14, I got deep into mathematics, and found it both easily intuitive and intensely mind-boggling that some of the many varieties of א aleph are rigorously demonstrably bigger than others. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 3, 2026, 10:51pm UTC](https://boards.straightdope.com/t/infinite-universe/1026295/87 "2026-01-03T22:51:25Z")
I think there are some fairly solid predictions that would require ludicrous levels of energy to test? But I’m not sure about that. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [January 3, 2026, 10:57pm UTC](https://boards.straightdope.com/t/infinite-universe/1026295/88 "2026-01-03T22:57:38Z")
IIRC I read it would need a cyclotron the size of earth’s orbit around the sun. Maybe someday. 🤞 ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [January 3, 2026, 11:03pm UTC](https://boards.straightdope.com/t/infinite-universe/1026295/89 "2026-01-03T23:03:21Z")
> [@Whack-a-Mole](#): > > IIRC I read it would need a cyclotron the size of earth’s orbit around the sun. Size of the galaxy is what googling the issue gets me. ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [January 3, 2026, 11:05pm UTC](https://boards.straightdope.com/t/infinite-universe/1026295/90 "2026-01-03T23:05:18Z")
> [@Half\_Man\_Half\_Wit](#): > > What I’ve said doesn’t depend on whether there is computation happening, just that one model of producing random numbers is via infinite computations as described, and that having access to randomness allows computations otherwise feasible with such infinite means. Here’s what you actually said: > [@Half\_Man\_Half\_Wit](#): > > if you believe there is true randomness in physics—again, something our best current models tell us is the case—then there is something at least equivalent to such infinite machinery at work You’re either making an empirical claim – of randomness entailing infinite machinery – or else “equivalent to” is meaningless here. Anyway, I’ll leave it there because I don’t want another thread spoiled. Go ahead have the last word or whatever. ---
**Author:** ![Half\_Man\_Half\_Wit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/half_man_half_wit/32/21766_2.png) [@Half\_Man\_Half\_Wit](https://boards.straightdope.com/u/Half_Man_Half_Wit)\ **Post date:** [January 3, 2026, 11:52pm UTC](https://boards.straightdope.com/t/infinite-universe/1026295/91 "2026-01-03T23:52:07Z")
> [@Mijin](#): > > You’re either making an empirical claim – of randomness entailing infinite machinery – or else “equivalent to” is meaningless here. Unless ‘equivalent to’ means ‘exactly that thing and nothing else’, I don’t get your meaning here. It’s as I wrote, there is something equivalent (in computational power, as clarified) to an infinitary process at work where random numbers are produced, because we know that such processes can produce random numbers. That does in no way entail a claim that there is any infinitary machinery present. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 4, 2026, 12:29am UTC](https://boards.straightdope.com/t/infinite-universe/1026295/92 "2026-01-04T00:29:56Z")
Just because I haven’t encountered this particular line of thought before, how would an infinite computer produce randomness? ---
**Author:** ![EllisDee](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ellisdee/32/4531_2.png) [@EllisDee](https://boards.straightdope.com/u/EllisDee)\ **Post date:** [January 4, 2026, 4:55am UTC](https://boards.straightdope.com/t/infinite-universe/1026295/93 "2026-01-04T04:55:31Z")
> [@Exapno\_Mapcase](#): > > Nobody has addressed this, and I was puzzled because I know I’ve heard the infinite universe mentioned for a long time. I’m pretty sure what happened is that the laymen books I read did present the universe as infinite as a possibility, but I dismissed the idea entirely and justified it by the fact that it was not stated definitively. For all I know, _every_ book I read did this and I just kept dismissing it each time. It’s not so much that I forgot, it’s that I chose to never accept the “possibility.” In one ear and out the other, as it were. Compounding this (for me) would be all the talk of how big the universe was x seconds after the Big bang. Like right now if you Google how big the universe was one second after the Big bang it will say 10 light years in diameter. But apparently those factoids are just about how big the _observable_ universe was at whatever time after the big bang. As an example, googling tells me the shortest time we can describe after the big bang is called the Planck epoch (10^-43 seconds), and then if I Google what the density of the universe was at the Planck epoch I get this: > During the Planck Epoch, the universe was unimaginably dense, approaching the Planck density (around 10^93 to 10^94 grams per cubic centimeter), where all four fundamental forces were unified and physics as we know it breaks down, requiring a theory of quantum gravity to fully understand its extreme conditions. > > - **Planck Scale** : The universe was at the Planck length (10^-35 meters) and Planck time (10^-43 seconds), the smallest meaningful units of length and time in physics. Except “the universe” _wasn’t_ at the Planck length and Planck time. The _observable_ universe was. “The universe” was infinitely large. So an infinitely large universe all at Planck density. Honestly, it boggles the mind. Or my mind, at least. You can see how the wording easily confused me. I don’t know why it doesn’t explicitly say that that’s how big the observable universe was instead of sloppily just calling it the universe. Unless I am misunderstanding something here, which is always possible. Corrections welcome. ---
**Author:** ![Half\_Man\_Half\_Wit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/half_man_half_wit/32/21766_2.png) [@Half\_Man\_Half\_Wit](https://boards.straightdope.com/u/Half_Man_Half_Wit)\ **Post date:** [January 4, 2026, 7:19am UTC](https://boards.straightdope.com/t/infinite-universe/1026295/94 "2026-01-04T07:19:26Z")
> [@Chronos](#): > > Just because I haven’t encountered this particular line of thought before, how would an infinite computer produce randomness? A computer capable of traversing infinitely many steps in finite time (sometimes called a [Zeno machine](https://en.wikipedia.org/wiki/Zeno_machine)) can solve the halting problem for any ordinary Turing machine, and therefore, successively enumerate that TMs [halting probability](https://en.wikipedia.org/wiki/Chaitin%27s_constant), an algorithmically random number. ---
**Author:** ![PlaceboTarget](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/placebotarget/32/1073_2.png) [@PlaceboTarget](https://boards.straightdope.com/u/PlaceboTarget)\ **Post date:** [January 4, 2026, 9:38am UTC](https://boards.straightdope.com/t/infinite-universe/1026295/95 "2026-01-04T09:38:29Z")
I sometimes wish I had the kind of mathematical mind Gauss or Euler possessed, one capable of producing a formula that could tell us whether the universe is truly infinite. Instead, I’m left with my imagination. I’m usually a realistic, practical person, yet lately my imagination has become my favorite place to be. The sheer amount of dark energy in the universe astonishes me. If it belongs solely to the visible universe, then we know almost nothing about it and should be careful not to leap to conclusions. But if dark energy originates in regions we can’t see (or from some higher reality beyond our reach) then imagination might be the only tool we have to even approach the mystery. As for me, I’ve long believed that what we call “the universe” (both the visible slice and whatever lies beyond) is just a speck in the spacetime of a far larger, turbulent reality we’ll never fully grasp. And when the exceptionally stable climate of the Holocene eventually comes to an end, there will be no one left to care whether the universe is infinite. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [February 15, 2026, 7:51am UTC](https://boards.straightdope.com/t/infinite-universe/1026295/96 "2026-02-15T07:51:01Z")
> [@Andy\_L](#): > > I don’t know whether String Theory is _disprovable_ - you could always add a new reason that the expected evidence didn’t show up. But that’s a classic problem with science - what counts as disproving. When we consider the wave/particle duality of matter are we _really_ thinking that particles are both at the same time or is it more likely we really do not understand their true nature but the math works really well for most things so just go with that? Like Newtonian physics works for most things but not all things. Is String theory _better_ at predictions even if we can’t say for certain it is the final answer? Heck, since Relativity and Quantum Theory are at odds can we say they are the final answer? Can we ever get a final answer? Or just ever more refined models (like getting to absolute zero…we can get closer and closer but never quite there…same with light speed). ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [February 15, 2026, 9:36am UTC](https://boards.straightdope.com/t/infinite-universe/1026295/97 "2026-02-15T09:36:12Z")
> [@Chronos](#): > > If, as seems likely, the Universe will keep expanding forever, then the average distance between atoms will also increase, and thus the probability of interactions between atoms asymptotically approaches zero. I know this is a somewhat old post, but I’m curious about whether this is established fact. Space has always been expanding, but we nevertheless continue to have local clumping of matter, driven mostly by gravity. Hence the formation of galaxies, stars, and planets. Is the expansion of space a relevant factor even within the vast expanse of our own galaxy, let alone between atoms or molecules? ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [February 15, 2026, 10:25am UTC](https://boards.straightdope.com/t/infinite-universe/1026295/98 "2026-02-15T10:25:41Z")
Systems like galaxies and solar systems are not that “gravitationally bound” in the long term and will fly apart. Now, an ever-expanding universe may have its density approach zero, but that does not rip apart any planets or atoms or anything like that, (barring some other mechanism); they will just be cold and dark and not very interesting, and they will be all alone as anything not gravitationally bound to them will be far away. The planets may themselves decay or evaporate or turn into black holes eventually. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 15, 2026, 12:28pm UTC](https://boards.straightdope.com/t/infinite-universe/1026295/99 "2026-02-15T12:28:50Z")
Even if the matter in local objects remains gravitationally bound, the energy won’t. Almost all of the electromagnetic energy produced in a galaxy leaves the galaxy, and almost all of it will never enter any other galaxy. And that electromagnetic energy gets spread thin, too (actually, spread even thinner than matter would). And you also need the energy to be present for patterns to recur. ---
**Author:** ![xtenkfarpl](https://avatars.discourse-cdn.com/v4/letter/x/c2a13f/32.png) [@xtenkfarpl](https://boards.straightdope.com/u/xtenkfarpl)\ **Post date:** [February 15, 2026, 2:52pm UTC](https://boards.straightdope.com/t/infinite-universe/1026295/100 "2026-02-15T14:52:29Z")
> [@Whack-a-Mole](#): > > When we consider the wave/particle duality of matter are we _really_ thinking that particles are both at the same time or is it more likely we really do not understand their true nature but the math works really well for most things so just go with that? That’s the core of the Bohr / Einstein debates at the Solvay Conference, of course. No attempt to ‘beat’ the uncertainty principle has ever panned out. So we end up with the Copenhagen interpretation: “shut up and calculate”. Philosophically unsatisfying though it is… [Previous page](https://boards.straightdope.com/t/infinite-universe/1026295.md?page=4) [Next page](https://boards.straightdope.com/t/infinite-universe/1026295.md?page=6)